G.3 Candidate program strategies. DODI 8120.2 describes three basic program
strategies plus a generic strategy called "other," encompassing variations,
combinations, and alternatives to the three. DODI 5000.2 identifies similar
strategies, called acquisition strategies. The three basic strategies are
summarized below and in Figure 7.

b. Incremental. The "incremental" strategy (called "Preplanned Product
Improvement" in DODI 5000.2) determines user needs and defines the system
requirements, then performs the rest of the development in a sequence of
builds. The first build incorporates part of the planned capabilities, the
next build adds more capabilities, and so on, until the system is
complete.

c. Evolutionary. The "evolutionary" strategy (called "evolutionary" in both
DOD Instructions) also develops a system in builds, but differs from the
incremental strategy in acknowledging that the user need is not fully
understood and all requirements cannot be defined up front. In this strategy,
user needs and system requirements are partially defined up front, then are
refined in each succeeding build.